OBJECTIVE: The overall objective of this research is to provide basic toxicological information on ultrasound irradiation of the reproductive systems and pregnant uterus in the mouse. This information provides toxicological data similar to that used in studying other diagnostic and therapeutic modalities so that risk assessment can be evaluated in medical ultrasound practive. Quantitative relationships are being derived relating ultrasound irradiation parameters and delivery regimes to bioeffects incidence. By using a graded set of ultrasound parameters the conditions leading to reduction of bioeffects incidence to control levels is being established. Both pulsed and continuous wave delivery regimes are being studied. The interrelationship of these regimes can be assessed from the basic data being obtained. Delivery formats in the sense of organ specificity are being assessed so that specific organ or limited body region toxicological information is being obtained which is relevant to the bulk of medical practice using ultrasound. As the toxicological data are being acquired, some important bioeffects are being studied so as to delineate the mechanism of interaction of the biological system and the applied ultrasound.